Behçet's disease is a vasculitis characterised by its thrombotic tendency. In some patients, manifestations of vascular lesions may dominate the clinical picture instead of the classic triad. We describe a 13-year-old boy with a 1.5-year history of Behçet's disease presenting with complaints of acute abdominal pain, severe headache and decreased vision. His work-up revealed a saccular aneurysm of the distal abdominal aorta, thrombosis in the right common iliac, external iliac and femoral arteries, and thrombosis of the superior sagittal sinus. Aortoiliac bypass with a Dacron graft was performed with success. He also received cyclosporin A and anticoagulant therapy. Severe vasculitis may become overt at any age in patients with Behçet's disease. Early diagnosis and management is important to prevent morbidity and mortality.